Natural Selection Lesson 2: Selective Pressure

1 collaborator

lin xiang (Author)

WHAT IS IT

This model allows students to test how different numbers of visual predators affect the coloration evolution in a mouse population. The patterns in the model directly lead to the NGSS core idea LS4.B Natural Selection.

HOW TO USE

Input running time for the model
Choose an environment color and number of visual predators
Click "Start/Reset" to set up the model
Click "Run/Pause" to run or pause the model. Use "Run a day" to run the model for a hypothetical day.
The "population-color-distribution" chooser allows you to generate the same numbers of mice with each color variation (i.e., equal probability) or random numbers of mice with each color variation (i.e., random probability). This allows you to set a constant starting point when collecting data.

HOW DOES IT WORK

A population of mice live in the simulation window and are hunted by visual predators (if any). The mice's coat colors vary from dark brown (color number 31) to light brown (color number 38). Mice may reproduce when cumulating enough energy. At a 90% chance, the offspring's color will be the same as the parents'; at a 10% chance, the offspring's color will mutate to a different shade of brown.

CREDITS AND REFERENCES

This model is created by Dr. Lin Xiang at the University of Kentucky. If you mention this model in a publication, we ask that you include the citations below.

Xiang, L. (2023). Natural Selection Lesson 2: Selective Pressure. Department of STEM Education, University of Kentucky, Lexington, KY.

CC BY-NC-SA 4.0

This work is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 4.0 License. To view a copy of this license, visit https://creativecommons.org/licenses/by-nc-sa/4.0/.

Comments and Questions

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Click to Run Model

breed [mice mouse]
breed [predators predator]
turtles-own [energy labeled offspring]
patches-own [food ]
globals [n num-prey total-catches color-watched-mouse bk-color color-A color-B]

to setup
  clear-all
  setup-turtles
  setup-patches
  reset-ticks
end 

to setup-turtles

  (ifelse Population-color-distribution =  "Random probability"
    [create-mice 80
    [
    set color 31 + random 8
    set shape "mouse top"
    set size 2.75
    setxy random-xcor random-ycor
    set energy 20 + random 20
    ]]

    Population-color-distribution = "Equal probability"
      [set n  0
       repeat 8
        [create-mice 10
          [set color (item n [31 32 33 34 35 36 37 38])
          set shape "mouse top"
          set size 2.75
          setxy random-xcor random-ycor
            set energy 20 + random 20]

          set n n + 1]])
end 

to setup-patches
  ask patches [set pcolor Environment-color set food 1]
  set bk-color Environment-color
end 

to go   ; natural selection

  if Days = 0 [output-print  "Input a longer running time." stop]
  if ticks >= Days [output-print  "Has reached the defined running time." stop]

  diff-survival
  move
  forage
  dead
  reproduce
  regrow
  if count mice = 0 [output-print "All mice have died."  Stop]
  tick
end 

to move
  ask mice [
            fd 1
            if random 5 = 0
    [rt (random 45) lt (random 45)]
          set energy energy - 1
  ]
end 

to dead
  ask mice [if energy <= 0 [die]]
end 

to forage
  ask mice [if food = 1  [set energy (energy + 1.3) set food 0]]
end 

to reproduce
  ask mice [
    if energy >= 40
    [if random 100 < 30 [hatch 1
      [setxy random-xcor random-ycor
        set energy 20
        if random 100 < 10 [
          set color 31 + random 8
            ]
        if color < 31 [set color 31]
          if color > 38 [set color 38]]]
      set energy energy - 20
  ] ]
end 

to regrow
  ask patches with [food = 0]  [set food 1]
end 

to diff-survival

   if bk-color != Environment-color
  [ask patches [set pcolor Environment-color]
    set bk-color Environment-color]


  ask mice [
      if random 2500 < (abs (color - Environment-color) * Number-of-visual-predators) [die]
  ]
end

There are 6 versions of this model.

Uploaded by	When	Description	Download
lin xiang	almost 2 years ago	adjust the interface, add probability chooser	Download this version
lin xiang	almost 2 years ago	adjust the interface	Download this version
lin xiang	almost 2 years ago	adjust the interface	Download this version
lin xiang	almost 2 years ago	decrease the max number of predators from 20 to 10	Download this version
lin xiang	almost 2 years ago	Fix info typos	Download this version
lin xiang	almost 2 years ago	Initial upload	Download this version

Attached files

File	Type	Description	Last updated
Natural Selection Lesson 2: Selective Pressure.png	preview	Preview for 'Natural Selection Lesson 2: Selective Pressure'	almost 2 years ago, by lin xiang	Download

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